1. Field of the Invention
The present invention generally relates to a computer power management system, and in particular to a computer power management through detection of user presence.
2. Description of the Related Art
Computer systems use a display device such as a liquid crystal display (LCD), a cathode-ray tube (CRT), an electroluminescent (EL) display, a plasma display panel and the like, to display information to a user. A display device can consume a substantial amount of the total energy resource used by the computer system. The amount of power consumed by the display device is greater concern with portable computers since they must rely on a portable power source such as a battery to provide electrical power when an electrical power outlet is not readily accessible. In some portable computers, the display device such as LCD may consume between 30% to 40% of the total power demand of the computer.
Various power management systems are employed by computer systems to reduce the amount of power consumed. Some conventional computer systems use a timer based power management scheme that turns off the display device when no input activity has been present for a defined time (e.g., 5-30 minutes) and turns the display device back on when a user operates an input device such as a keyboard or a pointer device. The duration of idle time period the computer must wait before turning off the display device is typically set by a user. One problem associated with such timer based scheme is that if the user sets the duration of the idle time period to be a relatively long time (e.g., 15 minutes or more), valuable electrical power may be wasted from the time when the user leaves the computer unattended until the time when the display device is automatically powered down by the timer based power management.